This invention relates to a filter apparatus and method of its operation, particularly to a pressure filter and method for extracting liquids from wet slurry fluids and for producing a substantially-dry filter cake of the solid materials present in such slurry fluids.
In many industrial processes and other applications where a slurry of solids and liquids is produced, it becomes necessary to filter the slurry solids from the liquids so that these materials may be efficiently utilized or, alternatively, disposed in an environmentally-safe manner. To separate the solids from the liquids, a filter apparatus, such as a pressure filter, is often used. Known pressure filters generally include one or more pairs of filter plates capable of relative motion. The plate inlet is adapted for receiving the slurry while the filtered liquids, called the filtrate, are collected by means of the plate outlet which also provides the requisite support for a filter medium positioned between the filter plates. This arrangement permits a filtration chamber to be defined by the inlet plate and the filter medium when the plates are pressed together. In the usual production cycle of such a filter, slurry is introduced into the filtration chambers under pressure through one or more inlet port, whereby it distributes itself throughout the chamber. After the filtration chamber is filled with slurry, the filter executes a series of programmed operations, namely, washing and/or treating the contents of the chamber in a particular manner, as well as pressurizing the chamber to force the liquids from the slurry through the filter medium, leaving the slurry solids, consolidated in a substantially-dry filter cake, within the chamber. The chamber is then opened, allowing the dry filter cake to be removed therefrom.
In the filter apparatus of the type here discussed, the filter is operated in a batch mode; i.e. apparatus open, apparatus closed, slurry input, treatment of the slurry to develop a cake, apparatus opened, filter medium moved as cake is discharged and advanced to the next cycle position, and then repeating the above steps. Efficiency of a pressure filter can be measured in the dryness of the resulting filter cake or in the success in removing a desired liquid from the slurry as effluent. The overall efficiency is measured in the amount of equipment and peripheral utilities that may be needed to accomplish a filter cycle as well as the length of time required for a single filter operation.
A need therefor arises for pressure-filter apparatus capable of efficiently treating a variety of slurries in a quick and low cost method. Furthermore it is desireable to provide a pressure-filter apparatus that is energy-efficient and capable of producing a substantially-dry filter cake in a minimum amount of time.